Friction-controlled reentrant aging and fluidization in granular materials.

Area of Science:

• Physics
• Materials Science
• Nonlinear Dynamics

Background:

• Granular materials exhibit aging and densification under mechanical stress.
• This behavior is driven by frictional contacts and energy dissipation, differing from thermal glasses.
• Understanding these nonequilibrium dynamics is crucial for natural and industrial processes.

Purpose of the Study:

• To investigate the role of friction in controlling granular compaction dynamics.
• To construct a dynamic state diagram mapping compaction behavior based on strain amplitude and friction.
• To uncover the fundamental nonequilibrium mechanisms governing compaction, rheology, and aging in athermal disordered systems.

Main Methods:

• Utilizing discrete element simulations to model granular packings.
• Applying quasistatic cyclic shear to perturb the systems.
• Analyzing the dynamic state diagram to identify different regimes and transitions.

Main Results:

• A friction-dependent crossover strain was identified, separating aging and fluidized regimes.
• Friction exhibits nonmonotonic behavior, initially suppressing then promoting fluidization.
• A transition from intermittent, avalanche-like rearrangements to continuous, diffusive motion was observed.

Conclusions:

• Friction plays a dual role in granular aging, acting as both a stabilizing and fluidizing agent.
• The findings reveal general principles for how friction governs metastability and flow in athermal matter.
• This research links microscopic contact mechanics to macroscopic dynamics in systems like soils and seismic faults.